The GMAT and GRE are more similar than they are different. Most students who take both end up doing about the same on each. Business schools do not have a preference between the two (unless explicitly stated). Haas is the only top school that still says that it prefers the GMAT.

- first of all, definitely take a GMAT practice test before you decide

- here's an overview of the differences: https://www.manhattanprep.com/gre/resou ... v-gmat.cfm

- more articles about how to decide: https://www.manhattanprep.com/gmat/blog ... at-or-gre/

But... there really isn't that much difference between the two. Most people tend to get similar scores in each, so don't stress out about the decision.